The invention relates generally to liquid extraction, and more particularly to a system and method for extracting carrier liquid.
In an electrostatic imaging process, a copy of an original image is produced by forming a toner image from a latent electrostatic image, which is then transferred to a target substrate, such as paper. The latent electrostatic image is generated by initially charging a photoconductor to create a uniform electrostatic charge of a particular polarity over the surface of the photoconductor. As an example, the photoconductor can be charged by exposing the surface of the photoconductor to a charge corona. The uniformly charged surface of the photoconductor is then patterned by selectively directing a modulated beam of light, such as a beam of laser light, to form the latent electrostatic image. Using charged toner particles having opposite polarity of the photoconductor surface, the latent electrostatic image is developed into the toner image by applying the charged toner particles to the photoconductor surface, which selectively adhere to the photoconductor surface according to the latent electrostatic image.
There are two distinct types of electrostatic imaging machines. The first type of electrostatic imaging machines uses dry toner to form toner images. The second type of electrostatic imaging machines uses liquid toner to form the toner images. Liquid toner generally includes toner particles and charge director compounds that are dispersed in a dielectric hydrocarbon-based carrier liquid, such as hydrocarbon solvents sold under the name of ISOPAR, which is a trademark of the Exxon Corporation. The liquid toner may be formed within the machine by mixing concentrated toner solvent, charge director compounds and dielectric hydrocarbon-based carrier liquid.
Some electrostatic imaging machines that use liquid toner utilize an intermediate transfer media (ITM) drum to transfer toner images from the photoconductor to a target substrate. The ITM drum includes a blanket on the surface on the ITM drum, which is a material that allows the ITM drum to accept a toner image and to transfer the toner image to the target substrate. In these electrostatic imaging machines, after the toner image is transferred onto the blanket of the ITM drum, the carrier liquid of the toner image is typically extracted from the surface of the ITM blanket by a carrier liquid extraction system. A conventional carrier liquid extraction system includes one or more heating elements, a suction plenum and a condenser. The heating elements are located within the ITM drum, while the suction plenum and the condenser are located outside of the ITM drum. In operation, the heating elements increase the temperature of the ITM blanket, which evaporates the carrier liquid on the ITM blanket. The evaporated carrier liquid is drawn into suction plenum using pressure differences created by the suction plenum. The evaporated carrier liquid is then condensed by the condenser so that the carrier liquid can be collected for disposal.
A concern with the conventional carrier liquid extraction system is that the use of heating elements in the ITM drum to evaporate carrier liquid is not efficient with respect to power consumption. In addition, during an unexpected shutdown, the internally heated ITM drum may damage the ITM blanket due to post-shutdown increase in blanket temperature caused by the latent heat of the heating elements combined with the temperature differential between the heating elements, the inside of the drum and the outside of the drum during normal operation. Another concern is that some of evaporated carrier liquid, which is considered hazardous material, is not drawn into the suction plenum of the carrier liquid extraction system. Consequently, a significant amount of carrier liquid is released into the surrounding environment exposing operators, technicians and other personnel to the hazardous material.
In view of these concerns, there is a need for a system and method for extracting carrier liquid in an efficient manner such that power consumption is reduced and the amount of carrier liquid released into the surrounding environment is minimized without causing damage to heat sensitive components, such as the ITM blanket.
A system and method for extracting carrier liquid utilizes thermal energy generated above a surface from which the carrier liquid is being extracted. The thermal energy can be generated by a heating element positioned over the surface. The thermal energy is used to evaporate the carrier liquid on the surface so that the evaporated carrier liquid can be condensed for collection. The use of thermal energy generated above the surface allows the system to evaporate the carrier liquid in an efficient manner with respect to power consumption. In an embodiment, the heating element may be included in a housing structure along with a condenser so that these components can be packaged in a compact assembly, which may be included in an electrostatic imaging machine. The configuration of these components allows the system to reduce the amount of evaporated carrier liquid released into the surrounding environment.
A system for extracting carrier liquid in accordance with the invention includes an imaging component, a heating element and a condenser. The imaging component has a surface to receive the carrier liquid. The heating element, which can be positioned over the surface of the imaging component, is configured to generate thermal energy that is to evaporate the carrier liquid on the surface of the imaging component. The condenser is configured to condense the evaporated carrier liquid from the surface of the imaging component.
In an embodiment, the heating element and the condenser are operatively connected to a housing structure, which is configured to be positioned over the surface of the imaging component.
A method for extracting carrier liquid includes providing a surface with the carrier liquid, generating thermal energy above the surface, evaporating the carrier liquid on the surface using the thermal energy, and condensing the evaporated carrier liquid from the surface.